A printer has one or more tractor sets for continuously feeding paper along first and second paper paths. One tractor set may be pivoted between positions for feeding paper from the front or bottom of the printer along the first paper path. Where one tractor set is used, it may be removed from the first feed path and disposed along the second paper path to feed paper along the second paper path for printing. Where two tractor sets are provided, the second set is disposed along the second paper path to feed the paper along the second path for printing. The tractor sets are detachable and usable in each of the three tractor set feed positions. Other features include eccentric bearings, resilient roller assemblies, an integrally molded mainframe and a cartridge assembly having a one-way ribbon advance clutch and a tensioning device before the mobius loop.